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256 Engine Parts Measurements
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ZouLou
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Joined: Jun 01, 2008
Posts: 15
Location: St. Louis/Columbia MO

PostPosted: December 27, 2009, 9:46 pm    Post subject: 256 Engine Parts Measurements

Does anyone have a 256 piston and rod lying around? I could really use rod length measurements (hole center to hole center if possible) and on the piston a wrist pin hole to top edge of piston. I have a attached an image od the two measurements i need.

I need measurement C or A, B and Hole to Hole



I also need measurement A in this picture

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despecial
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Joined: Sep 26, 2009
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Location: D20000

PostPosted: December 28, 2009, 5:37 am    Post subject: Re: 256 Engine Parts Measurements

A....22mm piston wrist pin
B....34mm big end
C..136mm con rod centre to centre
D..?

A..?

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Last edited by despecial on December 29, 2009, 12:40 pm; edited 1 time in total
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ZouLou
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Location: St. Louis/Columbia MO

PostPosted: December 29, 2009, 1:19 am    Post subject: Re: 256 Engine Parts Measurements

Thanks a whole lot for those measurements. I am ordering a custom piston from Venolia and I think the pin placement is set for a 256 engine. I know the pin hole size is for sure. Here is the piston drawing.

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despecial
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PostPosted: December 29, 2009, 9:12 am    Post subject: Re: 256 Engine Parts Measurements

you should also be able to fit a complete crank-rod-piston assembly from a later model motor
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yamaman
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Joined: Jan 04, 2007
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Location: Perth Western Australia

PostPosted: December 29, 2009, 9:46 am    Post subject: Re: 256 Engine Parts Measurements

Despecial, you've put down the big end as 26mm pin.
Big end internal diameter is 34mm I think...........(well it's a 26mm pin & 34mm rod on the 447's anyway)

Edit: Just looked at Mikes, bearings suit all motors, so rod big end is 34mm.

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despecial
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Posts: 232
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PostPosted: December 29, 2009, 12:39 pm    Post subject: Re: 256 Engine Parts Measurements

youre right-ive just checked my table and ive given the crank pin diameter not the big end...will edit the post
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ZouLou
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Joined: Jun 01, 2008
Posts: 15
Location: St. Louis/Columbia MO

PostPosted: December 29, 2009, 5:37 pm    Post subject: Re: 256 Engine Parts Measurements

OK here is the whole story with this question. I have a '79 XS650 engine. I got a head ported by 650performance.com. The porting was designed by Harry Lillie and the Venolia pistons were designed by him too to work specifically with his head porting. I am going to get a set of Carillo rods made for my application to ensure max rod strength. So looking at the piston design I realized they are set up for 22mm pins which come on the 256 engines. According to Craig Weeks the 256 rod and piston were preferred by top tuners for their dwell time at TDC. I am hoping to get the Venolia pistons and then use 256 sized rods and have it all work together with my rephased 447 crank. Any help or suggestions is greatly appreciated.

-Kyle
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